1. Field of the Invention
The present invention is related to earth formation drilling operations, and more particularly, to methods and system apparatus for predicting performance of a drilling system for a given formation.
2. Discussion of the Related Art
From the very beginning of the oil and gas well drilling industry, as we know it, one of the biggest challenges has been the fact that it is impossible to actually see what is going on downhole. There are any number of downhole conditions and/or occurrences which can be of great importance in determining how to proceed with the operation. It goes without saying that all methods for attempting to assay such downhole conditions and/or occurrences are indirect. To that extent, they are all less than ideal, and there is a constant effort in the industry to develop simpler and/or more accurate methods.
In general, the approach of the art has been to focus on a particular downhole condition or occurrence and develop a way of assaying that particular condition or occurrence. For example, U.S. Pat. No. 5,305,836, discloses a method whereby the wear of a bit currently in use can be electronically modeled, based on the lithology of the hole being drilled by that bit. This helps a drilling operator determine when it is time to replace the bit.
The process of determining what type of bit to use in a given part of a given formation has, traditionally, been, at best, based only on very broad, general considerations, and at worst, more a matter of art and guess work than of science.
Other examples could be given for other kinds of conditions and/or occurrences.
Furthermore, there are still other conditions and/or occurrences which would be helpful to know. However, because they are less necessary, and in view of the priority of developing better ways of assaying those things which are more important, little or no attention has been given to methods of assaying these other conditions.
In accordance with one embodiment of the present disclosure, an apparatus for predicting the performance of a drilling system for the drilling of a well bore in a given formation includes a means for generating a geology characteristic of the formation per unit depth according to a prescribed geology model. The geology characteristic generating means is further for outputting signals representative of the geology characteristic, the geology characteristic including at least rock strength. The apparatus further includes a means for inputting specifications of proposed drilling equipment for use in the drilling of the well bore. The specifications include at least a bit specification of a recommended drill bit. Lastly, the apparatus further includes a means for determining a predicted drilling mechanics in response to the specifications of the proposed drilling equipment as a function of the geology characteristic per unit depth according to a prescribed drilling mechanics model. The predicted drilling mechanics determining means is further for outputting signals representative of the predicted drilling mechanics. The predicted drilling mechanics include at least one of the following selected from the group consisting of bit wear, mechanical efficiency, power, and operating parameters.
In another embodiment, the apparatus further includes a means responsive to the geology characteristic output signals and the predicted drilling mechanics output signals for generating a display of the geology characteristic and predicted drilling mechanics per unit depth. The display generating means includes either a display monitor or a printer. In the instance of the printer, the display of the geology characteristic and predicted drilling mechanics per unit depth includes a printout.
In another embodiment, a method for predicting the performance of a drilling system for the drilling of a well bore in a given formation includes the steps of a) generating a geology characteristic of the formation per unit depth according to a prescribed geology model and outputting signals representative of the geology characteristic, the geology characteristic including at least rock strength; b) obtaining specifications of proposed drilling equipment for use in the drilling of the well bore, the specifications including at least a bit specification of a recommended drill bit; and c) determining a predicted drilling mechanics in response to the specifications of the proposed drilling equipment as a function of the geology characteristic per unit depth according to a prescribed drilling mechanics model and outputting signals representative of the predicted drilling mechanics, the predicted drilling mechanics including at least one of the following selected from the group consisting of bit wear, mechanical efficiency, power, and operating parameters.
In yet another embodiment, a computer program stored on a computer-readable medium for execution by a computer for predicting the performance of a drilling system in the drilling of a well bore of a given formation includes a) instructions for generating a geology characteristic of the formation per unit depth according to a prescribed geology model and outputting signals representative of the geology characteristic, the geology characteristic including at least rock strength; b) instructions for obtaining specifications of proposed drilling equipment for use in the drilling of the well bore, the specifications including at least a bit specification of a recommended drill bit; and c) instructions for determining a predicted drilling mechanics in response to the specifications of the proposed drilling equipment as a function of the geology characteristic per unit depth according to a prescribed drilling mechanics model and outputting signals representative of the predicted drilling mechanics, the predicted drilling mechanics including at least one of the following selected from the group consisting of bit wear, mechanical efficiency, power, and operating parameters.
Still further, in another embodiment, a display of predicted performance of a drilling system suitable for use as guidance in the drilling of a well bore in a given formation is disclosed. The display includes a geology characteristic of the formation per unit depth, the geology characteristic having been obtained according to a prescribed geology model and includes at least rock strength. The display further includes specifications of proposed drilling equipment for use in the drilling of the well bore. The specifications include at least a bit specification of a recommended drill bit. Lastly, the display includes a predicted drilling mechanics, the predicted drilling mechanics having been determined in response to said specifications of the proposed drilling equipment as a function of the geology characteristic per unit depth according to a prescribed drilling mechanics model. The predicted drilling mechanics include at least one of the following selected from the group consisting of bit wear, mechanical efficiency, power, and operating parameters.
Further with respect to the display of the predicted performance, the geology characteristic further includes at least one graphical representation selected from the group consisting of a curve representation, a percentage graph representation, and a band representation, and the display of the predicted drilling mechanics includes at least one graphical representation selected from the group consisting of a curve representation, a percentage graph representation, and a band representation.
The present embodiments advantageously provide for an evaluation of various proposed drilling equipment prior to and during an actual drilling of a well bore in a given formation, further for use with respect to a drilling program. Drilling equipment, its selection and use, can be optimized for a specific interval or intervals of a well bore in a given formation. The drilling mechanics models advantageously take into account the effects of progressive bit wear through changing lithology. Recommended operating parameters reflect the wear condition of the bit in the specific lithology and also takes into account the operating constraints of the particular drilling rig being used. A printout or display of the geology characteristic and predicted drilling mechanics per unit depth for a given formation provides key information which is highly useful for a drilling operator, particularly for use in optimizing the drilling process. The printout or display further advantageously provides a heads up view of expected drilling conditions and recommended operating parameters.